Packet-switching technology has been advantageously applied to optical communication systems. In packet-switched networks operating at low transmission speeds, the collisions between advancing packets are resolved by buffering the colliding packets until the output link becomes available. Such a scheme is commonly referred to as store-and-forward routing. Since large optical memories are expensive, today's solution for networks that use optical communication is to convert the optical signal to an electrical signal for appropriate buffering and queuing.
While the buffering and queuing techniques have met with some success for optical communication systems, such techniques become commercially impractical when data transmission speeds increase into the Gbps range. This is because of the optical-to-electrical conversion required. Some alternatives to the store-and-forward scheme have been proposed. One such alternative, commonly referred to as "hot-potato" routing, assumes no buffers in the switching nodes. Whenever two or more packets are about to collide, one packet is forwarded to the desired output and other packet or packets are forwarded to another output, which may not be the best route to the packet destination node.
In general, the switching node of "hot-potato" topologies must have the same number of input and output links. Some examples of networks that utilize the "hot potato" scheme are The Manhattan Street Network (MSN) and Blazenet. Unfortunately, a Manhattan Street Network requires a very inflexible grid type of topology, and Blazenet is designed for wide-area network span.
The proposed invention also uses the "hot potato" routing. However, as opposed to MSN, for example, the proposed invention can be built on totally uncontained topologies. Moreover, because each path contains a reverse channel, the number of input and output paths to a switching node need not, necessarily, be equal.
A "hot-potato" switching scheme by the "loop-back" technique, as used in this invention is described in "Blazenet": "A Photonic Implementable Wide-Area Network," Department of Computer Science, Stanford University, Technical report No. STAN-CS-87-1185, Oct. 1987. The proposed invention deals with the local/metropolitan area networks, as opposed to wide-area networks in "Blazenet" the difference being the number of packets that are stored in the loop-back path and, consequently, the switching algorithm used by the switching nodes.